Observation of an exceptional point in a non-Hermitian metasurface

Nanophotonics

article

Sang Hyun Park¹  Teun-Teun Kim¹  Sung-Gyu Lee¹  Soojeong Baek⁴  Taewoo Ha³  Sanghyub Lee³  Bumki Min⁴  Shuang Zhang⁵  Mark Lawrence⁶ 

[1] Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS);Department of Physics, Sungkyunkwan University;Department of Energy Science, Sungkyunkwan University;Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST);School of Physics and Astronomy, University of Birmingham, United Kingdom;Department of Materials Science and Engineering, Stanford University

关键词: metamaterials;    non-Hermitian photonics;    exceptional point;    asymmetric polarization conversion;    phase singularity;   

DOI  :  10.1515/nanoph-2019-0489

学科分类：社会科学、人文和艺术（综合）

来源: De Gruyter

【 摘 要 】

Exceptional points (EPs), also known as non-Hermitian degeneracies, have been observed in parity-time symmetric metasurfaces as parity-time symmetry breaking points. However, the parity-time symmetry condition puts constraints on the metasurface parameter space, excluding the full examination of unique properties that stem from an EP. Here, we thus design a general non-Hermitian metasurface with a unit cell containing two orthogonally oriented split-ring resonators (SRRs) with overlapping resonance but different scattering rates and radiation efficiencies. Such a design grants us full access to the parameter space around the EP. The parameter space around the EP is first examined by varying the incident radiation frequency and coupling between SRRs. We further demonstrate that the EP is also observable by varying the incident radiation frequency along with the incident angle. Through both methods, we validate the existence of an EP by observing unique level crossing behavior, eigenstate swapping under encirclement, and asymmetric transmission of circularly polarized light.

【 授权许可】

CC BY